CAMBRIDGE, Mass.—Seeking to bring a third party into their
agreement to develop and commercialize a companion diagnostic (CDx) test for
patients with genetically defined cancers, Eisai Co. Ltd. and Epizyme Inc. have
selected Roche's Molecular Diagnostics unit to supply the requisite technology
and platform.

On Jan. 7, the companies announced a collaboration to
develop an in-vitro polymerase chain
reaction (PCR)-based CDx test, with the goal of enabling the identification of
lymphoma patients with non-wild type EZH2, including the Y641 mutation. The CDx
will be used to detect the EZH2 mutation in subjects to determine enrollment
eligibility for dosing with a compound that Epizyme and Eisai are developing.

"Roche is a company that possessed world-class cutting-edge
technology and know-how, and has a proven history of companion diagnostic
approvals," says Lynn W. Kenney, senior director of corporate communications
for Eisai, of the company's decision to bring Roche into the fold.

Epizyme and Eisai announced their collaboration in March
2011. That agreement gave Epizyme $6 million up front, with the potential to
earn more than $200 million in additional research, development and sales
milestones, and up to double-digit royalties. Eisai agreed to fund 100 percent
of the R&D costs through human proof-of-concept, at which point Epizyme has
the right to opt into a profit-sharing and co-commercialization arrangement for
the United States.

In a September 2012 Nature
Chemical Biology paper, "A selective inhibitor of EZH2 blocks H3K27
methylation and kills mutant lymphoma cells," Epizyme reported that lymphomas
with genetic alterations of EZH2 require EZH2 enzymatic activity for
proliferation, and suggested that EZH2 is a driving oncogene in these cancers
and therefore an important therapeutic target.

Ultimately, if the compound is successful in clinical
studies and receives regulatory approval, the parties hope to make a companion
diagnostic available to help physicians identify patient candidates with the
EZH2-related mutation who may be likely to benefit from the approved drug.

"Our collaboration with Epizyme and Eisai highlights Roche's
position as the partner of choice for the development and commercialization of
companion diagnostics for personalized healthcare," said Paul Brown, head of
Roche Molecular Diagnostics, in a statement. "We are excited to be developing a
diagnostic test that will support Epizyme and Eisai in the development of an
EZH2 inhibitor as a new therapeutic for patients with genetically defined
lymphomas."

The companies declined to comment on the commercial
potential of the test.